This invention relates to an automobile heating, ventilation and air conditioning (HVAC) system.
There has been proposed an automobile heating, ventilation and air conditioning system (HVAC system) including a casing, a scroll chamber defined within the casing and having a blower fan, and an air passage defined within the casing and permitting air discharged from the blower fan to flow therethrough. The air passage includes a descending air passage through which the air from the blower fan flows downward, an ascending air passage through which the air fed from the descending air passage flows upward, and a communication air passage communicating the descending air passage with the ascending air passage. A heat exchanger for cooling the air from the blower fan, which is hereinafter referred to as a cooling heat-exchanger, is substantially horizontally disposed within the descending air passage. Another heat exchanger for heating the air passing through the cooling heat-exchanger, which is hereinafter referred to as a heating heat-exchanger, is disposed within the ascending air passage. A bypass air passage bypassing the heating heat-exchanger is disposed within the ascending air passage. The heating heat-exchanger is juxtaposed to the cooling heat-exchanger within the casing. Disposed within the communication air passage is an air-mix door for controlling a proportion of the air entering into the heating heat-exchanger, to the air entering into the bypass air passage. The casing has an inner wall defining the scroll chamber and the descending air passage. The inner wall is formed with a recessed portion disposed between the scroll chamber and the descending air passage. The recessed portion is recessed toward the descending air passage and exposed to the ascending air passage. A foot vent passage for permitting the air flow in a foot vent mode is disposed on the ascending air passage side of the recessed portion. A vent outlet and a defroster outlet, which are adapted to be open in vent and defroster modes, respectively, are disposed on an upper part of the ascending air passage. Such the HVAC system is disclosed in Japanese Patent Provisional Publication No. 8-282245.
In general, the automobile compartment tends to be exposed to high temperature in summer, for instance, during parking under sun heating. Therefore, it is required to increase an amount of cool air in full cool state in the vent mode, in which the whole amount of cool air passing through the cooling heat-exchanger flows through the bypass air passage. If a high-power motor of the blower fan is used for fulfilling the requirement, the HVAC system will be enlarged in size and the noise resulting from the increased amount of air discharged from the blower fan will become large. There is a demand for improving reduction of the noise in full cool state in the vent mode.
However, since in the above-described conventional technique, the bypass air passage of the ascending air passage is greatly curved to bypass the heating heat-exchanger, the bypass air passage is not linearly aligned with the vent outlet. This will cause high ventilation resistance in the bypass air passage in full cool state in the vent mode and, therefore, will prevent a smooth flow of the cool air passing through the bypass air passage, resulting in reduction of the amount of cool air and increase in the noise in the vent mode. If the bypass air passage and the vent outlet are linearly aligned with each other so as to permit a generally straight flow of the cool air in order to eliminate the reduction of the cool air amount and the increase in the noise, the upper part of the ascending air passage, which is disposed upward, namely downstream of the heating heat-exchanger and the bypass air passage juxtaposed to the heating heat-exchanger, will be required to largely increase in width. This will disturb the dimensional reduction of the casing and then that of the HVAC system as a whole.